The present invention relates to an electronic engine fuel injection control system.
In a known diesel engine electronic fuel injection control system which uses an electronically controlled, distributor diesel fuel injection pump, such as made by Stanadyne, fuel injection timing and amount is controlled by a solenoid operated poppet or xe2x80x9cspillxe2x80x9d valve. When the spill valve solenoid is not energized the spill valve is open and no fuel will be injected by the pump. When the spill valve solenoid is energized the spill valve closes and fuel will be injected by the pump. An electronic control unit includes a microprocessor controlled driver circuit which generates and applies a driver current to the solenoid of the spill valve. This driver current is rapidly ramped to a high current level and held near that level for a shutoff time period slightly shorter than the time required to close the spill valve. The driver current is then decreased to near a lower level and held near that lower level for a variable time period in order to hold the spill valve closed so that the pump can deliver a desired amount of fuel to an engine cylinder fuel injector at the proper time. The driver current is then rapidly ramped back down to zero amps in order to open the spill valve and terminate delivery of fuel to the engine cylinder fuel injector. The actual valve closure time can be effected by various factors, such as the impedance and resistance of wiring harnesses, valve stroke settings, valve stroke changes, supply voltage variations, variations between different fuel injection pumps, variations from one cylinder to cylinder within a fuel injection pump, and variations in engine speed, load and timing. It would be desirable to control the spill valve to compensate for such variations and to thereby achieve consistent and predictable spill valve closure timing.
Accordingly, an object of this invention is to provide a system for accurately controlling a spill valve of an engine fuel injection unit.
These and other objects are achieved by the present invention, wherein an engine has a fuel injection unit with a valve operable in response to a valve control signal to cause fuel to be injected into the cylinders, and a control unit which generates the valve control signal. A method of controlling the valve includes sensing a time associated with movement of the valve corresponding to start of a fuel injection event, and modifying the valve control signal as a function of the sensed time. The method further includes determining a rise time of the valve control signal, determining a valve operation delay time as a function of the rise time, determining a difference time representing a difference between a desired valve operation time and the sensed time, comparing the valve operation delay time to the difference time, and adjusting timing of the valve control signal as a function of the comparison. The method, also, as a function of the comparison, varies individual valve control signal parameter values, each associated with a particular cylinder of the engine, generates a sum value SUM representing a sum of the individual parameter values for all the cylinders, generates an average parameter AVE by dividing the SUM value by the number of cylinders, generates updated individual parameter values by subtracting the AVE value from previous individual parameter values, and modifies the valve control signal as a function of the updated individual parameter values and the AVE value.